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4D Physical Simulation of Basin-scale Salt Tectonic Processes and Coupled Depositional Systems
are inactive and sediment progradation on the outboard allochthonous
Figure 1: Thin-skinned Extension in a Passive Margin Sedimentary
salt nappe/canopy systems is again characterised by extensional
Wedge on Salt Substratum
deformation and formation of mini-basins on allochthonous salt levels.
In all of the stages, the interaction of gravity-driven deformation,
syntectonic sedimentation and salt mobilisation controls the
evolution of the basin. Not all passive margin salt basins have passed
through all three stages: most of the Cretaceous salt basins of
the South Atlantic margins of Brazil and Africa are actually in the
intermediate stage, whereas the Jurassic salt basins in the Gulf of
Mexico and Eastern Canada have reached the late evolutionary stage.
Salt Dynamics Group
Analogue modelling is an efficient tool for investigating salt tectonic
processes in laboratory-scaled experiments. In the analogue
experiments, brittle sediments are represented by sand, and salt by
silicone putties or silicone rubbers. This approach garnered strong
interest in petroleum exploration that focuses on structures in the
overburden overlaying the salt sediments. In the last two decades,
The Salt Dynamics Group has
A: Pressure gradient (P1–P2) in salt layer; B–D: Kinematic segmentation during gravitational spreading
(B: Early stage; C: Intermediate stage; D: Late stage); E: Experiment section with typical structures and related
recently developed a new
stratigraphic features in basin-scale framework (thin salt–moderate progradation–tilted basin).
generation of analogue
Figure 2: Passive Margin Salt-basin Experiment in Dalhousie Analogue
experiments with 3D strain
Model Deformation Laboratory
monitoring to support exploration
in frontier salt basins.
analogue modelling studies have significantly improved our
understanding of salt tectonics.
6,7
However, only a few studies have
addressed basin-scale salt tectonics from the shelf extensional domain
to the deep-basin contractional domain
8
or included appropriate
model time-scales to simulate natural passive margin sedimentation.
The Salt Dynamics Group has developed a new generation of physical
experiments with improved scaling and digital 3D deformation
monitoring that integrate geological data and the seismic
interpretation results of case studies into scaled physical experiments
(see Figure 2). For the first time, our physical experiments include the
realistic simulation of depositional scenarios with variable
sedimentation patterns and rates to simulate the evolution of salt
basins from the early post-rift stage to the modern margin, and from
the shelf to the deepwater slope and basin.
Gravity spreading and mobilisation of the viscous silicone layer in the
experiments generate complex 3D structures (see Figure 1E) similar
to those observed in passive margin salt basins, including crestal
Experiment surface evolution and 3D displacement field monitored by stereoscopic charge-coupled device
(CCD) cameras and digital image correlation (DIC). The experiment surface is shown with an overlay of the
grabens, landward and seaward dipping growth fault rollovers, 3D vector grid calculated by DIC.
reactive, passive and active diapirs, turtle structures, canopies and
allochthonous salt detachments. requires experiment durations of 10–14 days to simulate the
complete salt basin evolution over ~50 million years.
Experiment Set-up and Scaling
Previously published analogue models mainly focused on the The 3D experiments are performed on a rigid base. The experimental
structural evolution of salt structures and did not include a realistic set-up represents a passive margin sedimentary wedge that is
simulation of passive margin sedimentation scaled to the model. Our prograding over a post-rift salt basin (see Figures 2 and 3).
results demonstrated that the dynamically established time-scale Geological and geophysical data provide the boundary conditions
EXPLORATION & PRODUCTION – OIL & GAS REVIEW 2008 – VOLUME 6 ISSUE II
95
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